A clinical trial from the Mayo Clinic found that flaxseed failed to ease hot flashes among postmenopausal women.
Preliminary studies indicated that flaxseed might be a potentially effective treatment for hot flashes.
For example, an earlier study by the same Mayo Clinic investigators – which had no placebo group – indicated that 40 grams (1.4 ounces) of crushed flaxseed daily might help reduce hot flashes (Pruthi S et al. 2007).
Although flaxseed is perhaps the richest food source of plant-form omega-3s, its long-proposed potential for alleviating hot flashes and other adverse menopause side effects rest on its abundance of estrogenic fibers called lignans.
Preliminary evidence suggests that lignans' breakdown products may help prevent breast cancer (Saarinen NM et al. 2007).
However, that potential benefit seems to depend on a woman's genetic makeup … especially in premenopausal women (McCann SE et al. 2002).
Flaxseed fails to fight hot flashes in new trial
Led by Mayo Clinic researcher Sandhya Pruthi, M.D., the randomized, placebo-controlled study followed 188 women who consumed flaxseed or a placebo between October and December of 2009.
Some of the women were breast cancer patients and some were not.
Daily for six weeks, the women ate either one flaxseed bar (providing 410mg of lignans) or a placebo bar.
The participants completed daily hot flash diaries for one week before eating any bars, and then continued recording their daily hot flashes.
The results showed no statistically significant difference in the women's average hot flash scores between women eating flaxseed bars and those eating the placebo bars.
“While preliminary data from our 2007 pilot study showed a reduction in hot flashes associated with the consumption of ground flaxseed, our new study did not result in a significant decrease in hot flashes with eating flaxseed compared to placebo,” said Dr. Pruthi, who is based at Mayo Clinic's Breast Diagnostic Clinic.
Dr. Pruthi says patients shouldn't give up flaxseed if they enjoy it: “Flaxseed may be beneficial for people who want to add fiber and bulk to their diet to manage constipation, but more research is needed to identify whether flaxseed has any other health benefits.”
Frankly we're surprised she didn't mention that flaxseed and flaxseed oil are among the richest sources of short-chain, plant-source omega-3 ALA, which certainly does provide “other health benefits.”
Omega-3 ALA is shown to provide minor heart-health benefits, and the body can use it to make small amounts of the far more valuable long-chain omega-3s (EPA and DHA) found in fish fat and human cells.
McCann SE, Moysich KB, Freudenheim JL, Ambrosone CB, Shields PG. The risk of breast cancer associated with dietary lignans differs by CYP17 genotype in women. J Nutr. 2002 Oct;132(10):3036-41.
Mousavi Y, Adlercreutz H. Enterolactone and estradiol inhibit each other's proliferative effect on MCF-7 breast cancer cells in culture. J Steroid Biochem Mol Biol. 1992 Mar;41(3-8):615-9.
Pruthi S, Qin R, Terstreip SA, Liu H, Loprinzi CL, Shah TR, Tucker KF, Dakhil SR, Bury MJ, Carolla RL, Steen PD, Vuky J, Barton DL. A phase III, randomized, placebo-controlled, double-blind trial of flaxseed for the treatment of hot flashes: North Central Cancer Treatment Group N08C7. Menopause. 2011 Sep 1. [Epub ahead of print]
Pruthi S, Thompson SL, Novotny PJ, Barton DL, Kottschade LA, Tan AD, Sloan JA, Loprinzi CL. Pilot evaluation of flaxseed for the management of hot flashes.J Soc Integr Oncol. 2007 Summer;5(3):106-12.
Saarinen NM, Wärri A, Airio M, Smeds A, Mäkelä S. Role of dietary lignans in the reduction of breast cancer risk. Mol Nutr Food Res. 2007 Jul;51(7):857-66. Review.